MONDAY, March 31, 2014 (HealthDay News) -- Although steroids are often given to patients undergoing heart bypass surgery, a large new study suggests this common practice has no benefit and could actually be harmful.

Researchers found preventive steroids do not improve the outcome of these procedures and could put patients at greater risk for a heart attack after their surgery. The study authors said their findings challenge a practice doctors have used for decades.

The study is scheduled for presentation Monday at the annual meeting of the American College of Cardiology (ACC), in Washington, D.C. Because the study was presented at a medical meeting, it should be viewed as preliminary until published in a peer-reviewed journal.

"Based on these results, we suggest that steroids should not be used [as a preventive measure] during cardiac surgeries that require the use of cardiopulmonary bypass," lead investigator Dr. Richard Whitlock, an associate professor of cardiac surgery at McMaster University, in Hamilton, Ontario, Canada, said in an ACC news release.

During bypass surgery, patients are put on a "heart-lung machine." To reduce inflammation during and after this procedure, these patients frequently receive steroids.

Although use varies among countries, hospitals and surgeons, the researchers calculated that these patients are given steroids in about 25 percent of medical centers around the world.

To investigate whether steroids actually improve surgical outcomes, the researchers looked at information compiled on 7,500 patients who had heart bypass surgery at one of 82 medical centers. The hospitals included were spread out across 18 countries in Asia, Europe, the Middle East, North America and South America.

Half of the patients were randomly assigned to receive methylprednisolone -- a commonly used steroid to prevent inflammation during bypass surgery. The other half received a placebo, or fake medicine. The outcome of each procedure was analyzed 30 days after surgery. The researchers found that 927 of the study participants had a heart attack and 332 died.

The findings revealed that the steroid treatment had no significant benefit. The drug did not improve rates of death, heart attack, stroke, kidney failure or lung failure, according to the news release.

Patients who took steroids, however, had a 15 percent greater risk of death or heart attack, the researchers said. This group of patients also had a 21 percent higher risk of heart attack alone, the study found.

The reason preventive steroids increased the risk for heart attack is unclear, the researchers said. They said their findings apply only to steroids given to patients to prevent inflammation during bypass surgery. The study did not suggest that patients taking steroids for other medical reasons should stop taking them for heart surgery.

"As [heart] disease continues to climb, cardiac surgery has become a common operation worldwide," Whitlock said. "Trying to improve the outcome for these patients is clearly imperative, and it is important to re-evaluate practices for which there is a lack of evidence and potential for harm. This study shows that administering steroids during cardiac surgery requiring bypass can cause harm."